Piston-shaped vessel



FIG. 1 is a perspective view of a piston-shaped vessel showing my new design;

FIG. 2 is a front elevational view thereof, the rear view being identical to the front;

FIG. 3 is a right side view of the piston-shaped vessel of FIG. 1;

FIG. 4 is a top view of the piston-shaped vessel of FIG. 1; and,

FIG. 5 is a bottom view of the piston-shaped vessel of FIG. 1. 

The ornamental design for a piston-shaped vessel, as shown and described. 